More Protein, Fewer Calories: A Winning Combo, With Reservation

When seeking to get leaner, many athletes and lifters look to a high-protein, low-carb diet to achieve ideal results. However, there are questions as to whether such an approach may alter hormones or acid/base balance and thus reduce health or performance.

Study Design

All of the study participants were male. The researchers divided the subjects into two groups:

High Calorie Restriction Group: This group of eight participants decreased their daily caloric intake by 750 calories.

Low Calorie Restriction Group: The second group of seven subjects cut out 300 calories per day.

The plan was to maintain this restriction for four weeks while keeping protein levels high. In both groups, daily protein intake averaged around 2.1 grams per kilogram of bodyweight. The researchers tested the power of the participants before and after the four-week period. They also measured body composition, hormonal changes, and acid/base balance.

Results

The low-calorie-restriction group experienced no significant changes during the course of the study in any of the researched parameters. That’s not to say they didn’t get results, but the data wasn't considered statistically significant.

The high-calorie-restriction group, on the other hand, had a host of changes resulting from their diet.

Body Composition: They lost nearly five pounds during the four weeks, most of which was from fat. The researchers indicated the remaining weight loss was probably partially glycogen and water weight, meaning the subjects didn’t lose much or any muscle. Participants who began the study with a body fat percentage higher than ten percent loss much less lean mass than those who were already lean.

Acid/Base Balance: One potential downside the researchers found was a loss of calcium ions in the high-calorie-restriction group. The loss in calcium ions was probably due to the increasing acidity of the diet, which was caused by maintaining high protein but reducing carbohydrate sources that tend to be more alkaline. As a result, there was a modest but important reduction in bone mass as well.

In addition to losing weight, the high-calorie-restriction group improved performance. Both sprinting times and vertical jump performance improved. Note that these are relative power activities, meaning they involve moving the body around. The weight loss improved performance in these activities despite a minimal loss of muscle from calorie restriction in some cases. Additionally, subjects who started the study with more than ten-percent body fat experienced greater performance gains.

Application

While the acidosis and resulting loss of calcium were unfortunate side effects in this particular study, the researchers gave suggestions for people who want to reap the benefits without the pitfalls. They suggested increasing intake of “alkaline-generating foods, such as fruits and vegetables, or supplements high in either potassium or bicarbonate.” These changes will mitigate the acidosis and, subsequently, the loss of calcium.

Ultimately, losing about a pound of body weight each week over four weeks resulted in some mild acidosis and might cause muscle loss if you do not consume enough protein. However, it seems these downsides can be reduced by careful manipulation of the diet, leaving only the upsides of greater health and improved performance.